You could just use this: https://github.com/otaithleigh/VSR-B9PartSwitch-Cfgs/releases
It needs b9partswitch. But once you have it you can assign ven's tankbutts by rightclicking the engine. You'll have to reattach the engine once model changes, but the tankbutt won't disappear on flight reloads.

Small bug report on the new 5m cryo tanks. Their dry mass is set to only 3.6tons, which is equal to that of the long 3.75m tank. Presumably this is supposed to be a bit higher, since both 5m tanks are larger than the 3.75m tank. This also gives extra problems for the long 5m tank, since it contains so much hydrogen and is so light, that its dry mass actually goes negative when in pure hydrogen mode.
Based on the dimensions of the tanks I've set the short 5m tank to 4.8tons and the long one to 9.6tons, which is a bit more balanced and solves the negative mass issue.

Yea, that's accurate. It has to do with the density of LH2. You have a much higher isp, but because LH2 is so light, you have much less reaction mass. Note that your pure LH2 craft is much lighter than your hydrolox craft. If you make your LH2 tank bigger so that the masses of both craft are equal you'll see that the pure H2 craft has much higher dV.

Just for people who want to play with the ullage simulation functioning: The previous version (1.2.0.1) works with KSP 1.2.2 and has functioning ullage simulation. You can get it on spacedock by going to the changelog tab.

It's probably breaking stuff because it's recognizing something else as color tags. Any other identifiers to help narrow it down? Else you'll have to replace them one by one and check yourself if the adjustment is applicable. (Also, double check that the config is correct. I'd expect a </color> tag or something at the end if its based on HTML.)
You probably didn't tick the 'Regular Expression' box in search mode. Else it obviously isn't going to work.

Get notepad++. Load up the cfg file. ctrl+h. In the search box use:
\[#([0-9a-fA-F]+)\]
Then in the replace box use:
<color=#\1>
Make sure to set search mode to regular expression.
That should replace it with the correct syntax.
Can even open all files at once and replace it in all of them.

If you want to fly kerbal rockets in RSS or real rockets in stock, just multiply the ISP on all engines by sqrt(scale factor). That should give you approximately correct behaviour. So if you have a stock kerbal X rocket and you multiply all engine ISP's by ~3.15 it'll work just fine in RSS.

Just tested this out and it works like a charm! Loving it.
However, I noticed that persistent thrust does not seem to work when the vessel isn't active. So I can't set up a maneuver node with solar sail navigator, go do something else for a year and then come back to a probe in the desired orbit. Are there any plans to add this functionality in the future?

How about linking that video. Also, always use the install instructions on the front page, 3rd party instructions might be dated:
- Download a texture pack (2048, 4096 or 8192), extract and dump the contained RSS-Textures folder into Gamedata.
- Download the plugin, extract and dump the contained Kopernicus folder, RealSolarSystem folder, Modularflightintegrator folder and Modulemanager.dll into your gamedata folder.
If you did exactly that and it still doesn't work, report back

If you're going to blacklist MFT configured tanks you'll also have to exclude engines and RCS configured by Realfuels. Testing tweakscale + Realfuels some more shows that rescaled engines (RCS counts as engines) also go negative mass if downscaled. So I'm guessing the mass change gets applied twice in that case as well.

Then you should probably be asking this question on the 64k scale mod. I'm guessing you didn't properly follow the instructions of kscale64:
"Installation Instructions
Full installation instructions are included in the download.
You must download SigmaDimentions for this mod to work correctly. This can be downloaded from https://github.com/Sigma88/Sigma-Dimensions/releases"
If you really only have Kopernicus, 6.4 and a texture (What texture? 64k shouldn't have textures) then you definitely didn't follow the instructions.

By the way, while we're on the subject of tweakscale bugs:
I think you have some boundary condition error for the scaling. If you scale a fuel tank the indicator goes 7.5 --> 10 (full green bar) --> 10(full green bar) --> 20 while the actual size goes 7.5 --> 10 --> 20 --> 20. If you set freescale to false in the DefaultScales.cfg it works as expected, so it's probably something in the freescale code.

Hey Nathan. Something is definitely iffy with tweakscale + RF integration.
So far I've narrowed it down to a small tank (Oscar B tank) rescaled to 0.4m going NaN when drained to about 50%. Before draining to that point everything works just fine. Tested on an install containing RSS (Shouldn't affect stuff), Engineer (shouldn't affect stuff), Procedural fairings (again, no influence), Ven's stock revamp (for the eyecandy) and of course Realfuels + tweakscale.
Here's a copy of my log in which I discovered said bug. The relevant bit is this stuff here:
After that first mention of a NaN everything predictably goes to excrements as the NaN spreads throughout the ship and demolishes everything. Considering that the bug only occurs when the tanks start to empty means it's probably something with the mass going to 0.
Looking at the offending tank in the VAB with engineer you can see this is indeed the case
In fact, testing it with several other tanks shows that many of the smaller tanks go negative mass when scaled down. Definitely something not working correctly here.
Edit: Just tested with a completely barebones install. Only tweakscale as it comes out of the box, Realfuels as it comes out of the box (no engine configs) and Engineer to see masses. Negative mass problem persists when downscaling tanks.

I've been having issues with the tweakscale + Realfuels combo that might be related with the MFT issues people above me described.
So far I've narrowed it down to a small tank (Oscar B tank) rescaled to 0.4m going NaN when drained to about 50%. Before draining to that point everything works just fine. Tested on an install containing RSS (Shouldn't affect stuff), Engineer (shouldn't affect stuff), Procedural fairings (again, no influence), Ven's stock revamp (for the eyecandy) and of course Realfuels + tweakscale.
Here's a copy of my log in which I discovered said bug. The relevant bit is this stuff here:
After that first mention of a NaN everything predictably goes to excrements as the NaN spreads throughout the ship and demolishes everything. Considering that the bug only occurs when the tanks start to empty means it's probably something with the mass going to 0.
Looking at the offending tank in the VAB with engineer you can see this is indeed the case
In fact, testing it with several other tanks shows that many of the smaller tanks go negative mass when scaled down. Definitely something not working correctly here.
Edit: Just tested with a completely barebones install. Only tweakscale as it comes out of the box, Realfuels as it comes out of the box (no engine configs) and Engineer to see masses. Negative mass problem persists when downscaling tanks.

Yes. Parts that use stock textures will look broken. But since KSP is 64 bit now, you don't really need to. In ye olde days it was a trick to save a few dozen Mb's, now its better to just keep the old textures.
No, you'll have to run the unpruner file. But again, don't use the pruners anymore. No real point.